Question: Simplify the following expression: $y = \dfrac{5}{7z} - \dfrac{1}{2z}$
Solution: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $7z$ and $2z$ $\lcm(7z, 2z) = 14z$ $ y = \dfrac{2}{2} \cdot \dfrac{5}{7z} - \dfrac{7}{7} \cdot \dfrac{1}{2z} $ $y = \dfrac{10}{14z} - \dfrac{7}{14z}$ $y = \dfrac{10 -7}{14z}$ $y = \dfrac{3}{14z}$